For personal authentication based on a fingerprint, various methods of inputting a pattern as an image into a computer by using a laser or the like and analyzing the pattern image have been developed up to the present date in place of an old-established method based on visual check. A large number of techniques for a sensor section for detecting a fingerprint have been proposed; for example, there have been practically used an optical method of directly taking a fingerprint pattern into an image sensor by combining the difference in scattering angle between a ridge and a recess with a total reflection condition and a method of extracting a pattern by utilizing a semiconductor sensor for detecting the difference in charge distribution on a contact surface. Furthermore, a method of extracting a vein pattern of a fingertip or a palm by using near-infrared light to perform personal authentication has been proposed and the product using the method has been manufactured (e.g., Patent document 1-3). Since a fingerprint pattern is more complicated in shape compared with a vein pattern, the methods have a possibility of constituting a personal authentication system with higher accuracy. However, there is a risk that authentication may be violated by counterfeiting the same shape as a finger pad, for example, by transcribing a fingerprint to a mold made of a material such as silicone.
When a laser beam is irradiated to a living body, an intensity distribution of reflected and scattering light forms dynamic laser speckles (random speckled pattern) due to moving scattering particles such as blood cells. It is known that this pattern is detected on an imaging plane by an image sensor, and time variation of the pattern at each pixel is quantified and displayed in the form of a map, whereby a bloodstream distribution of capillary blood vessels in the vicinity of the surface of the living body can be imaged. Using such a phenomenon, a certain number of techniques and devices for measuring a bloodstream map of a subcutaneous layer or an ocular fundus have been proposed by the present inventors (e.g., Patent document 1-3).
The present inventors accomplished inventions of combining the bloodstream map disclosed in the above-mentioned documents and a fingerprint pattern for performing personal authentication, and have already proposed them (Patent document 10 and 11). In these patent documents, authentication of a finger of a living person is performed using phenomenon that, when the bloodstream of a fingertip is imaged using a laser bloodstream imaging method, a fingerprint pattern appears in a bloodstream map since a bloodstream in a recess portion of the fingerprint is faster than that in a ridge portion (Patent Document 10). Also, there has been proposed a method of detecting the internal bloodstream distribution of a finger by using a near-infrared laser light so as to improve accuracy on personal authentication and exclusion of other persons or a method of determining a living finger or an imitated finger by analyzing a waveform of the bloodstream since the bloodstream of a fingertip varies in synchronism with heart beat (Patent document 11).
However, these methods are still problematic in that, when a very thin silicone film having a counterfeited fingerprint with ridge-and-recess pattern is affixed to a surface of finger, a sensor perceives the bloodstream of the finger behind the film and determines it wrongly as being alive. Also, there is a problem that, in winter season with a low room temperature, a living finger is wrongly determined as a counterfeited finger since the fingertip becomes cold, the bloodstream of the surface thereof decreases and the waveform of the bloodstream becomes difficult to be detected. To the best of the present inventors' knowledge, there has not yet been proposed any method and device to overcome these problems described above.    Patent document 1: JP-A-5-73666 (JP-A denotes a Japanese unexamined patent publication)    Patent document 2: JP-A-8-16752    Patent document 3: JP-A-2003-331268    Patent document 4: JP-B-5-28133 (JP-B denotes a Japanese examined patent publication)    Patent document 5: JP-B-5-28134    Patent document 6: JP-A-4-242628    Patent document 7: JP-A-8-112262    Patent document 8: JP-A-2003-164431    Patent document 9: JP-A-2003-180641    Patent document 10: WO05/122896    Patent document 11: WO07/097,129